Cat tree building block element



FIG. 1 is a top perspective view of the cat tree building block element of our ornamental design;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a rear elevation view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a left side view thereof;

FIG. 7 is a top plan view thereof;

FIG. 8 is a bottom plan view thereof;

FIG. 9 is a perspective view of an exemplary cat tree formed using the cat tree building block element shown in FIGS. 1-8; and,

FIG. 10 is another perspective view of FIG. 9.

The broken lines representing a connector element are for illustration only and form no part of the claim. 

CLAIM We claim the ornamental design for the cat tree building block element, as shown and described. 